The GAP will lose popularity, and be hard to find, if people don't buy it and use it. Are you in a position to spend the money to help keep it popular and active?
Personally I like the 45GAP. It's fun to shoot, and I have no problem controlling it.
I have a 1911 ACP that I keep in my bedroom for home defense. I bought it because I like history, and historical Items. Therefore I would never mod. it, or make it a "race gun". If I wanted to do that, I would probably go with an XD GAP or 9. (Punch, vs. Controllability).
I like the.40sw. Though I've always felt that from the beginning, it was a compromise round. Cheaper to shoot than GAP or 357Sig, without the larger diameter, or super penetration.
My XD is in 357Sig. I bought it as a car/travel weapon. If I'm not in my home, and if for some God forsaken reason I would ever have to "have it out" while "out and about", I want something more offensive. The 357Sig was chosen by the Secret Service and the Texas DPS because of its' ability to punch through barriers and still smack what it finds behind it.
The GAP is a great self-defense round, and I enjoy shooting it. The real question, I feel for you, is are you comfortable enough with the .40sw to trust your life to it. Or, do you feel the GAP is enough "better" to warrant the extra cost.